Motorists drive past a gas station in Los Angeles Thursday, Oct. 4, 2012. Motorists in California paid an average of $4.232 per gallon Wednesday. That is 45 cents higher than the national average and exceeded only by Hawaii among the 50 states. (AP Photo/Damian Dovarganes)

Lee Huffman removes a gas hose after delivering gas to the Costco gas station in Lodi, Calif. Thursday, Oct. 4, 2012. Throughout California the average price of a gallon of regular gasoline jumped 8 cents overnight to $4.32 and was up 18 cents during the past week, according to the AAA's Dailey Fuel Gauge. Motorists who gassed up at this location paid $3.93 per gallon.(AP Photo/Rich Pedroncelli)

SAN FRANCISCO (AP) — Californians woke up to a shock Friday as overnight gasoline prices jumped by as much as 20 cents a gallon in some areas, ending a week of soaring costs that saw some stations close and others charge record prices.

The average price of regular gas across the state was nearly $4.49 a gallon, the highest in the nation, according to AAA’s Daily Fuel Gauge report.

In Southern California, the price jumped 20 cents a gallon overnight to $4.53 in Ventura. And in the Los Angeles-Long Beach area prices went up 19 cents to nearly $4.54. And it wasn’t any better to the north, as a gallon of regular gas in San Francisco averaged nearly $4.60.

In many areas, prices have jumped 40 cents in a week as refinery problems have created shortages and helped send wholesale prices soaring. Some stations ran out of gas and shut down Thursday rather than pay those costs.

Even Costco, the giant discount store chain that sells large volumes of gas, decided to close some stations, the Los Angeles Times reported.

"We do not know when we will be resupplied," read a sign at one Southern California Costco, according to the Times.

Other gas stations charged more than $5 a gallon. The Low-P station in Calabasas charged $5.69 Thursday. The pumps bore hand-written signs reading: "We are sorry, it is not our fault," the Times said.

While gas prices have spiked around the nation, refinery outages and pipeline problems have added to woes in California.

Among the recent disruptions, an Aug. 6 fire at a Chevron Corp. refinery in Richmond left one of the region’s largest refineries producing at a reduced capacity. A power failure in Southern California has affected an Exxon Mobil Corp. refinery, and a Chevron pipeline that moves crude to Northern California also was shut down.

The national average for gas is about $3.79 a gallon, the highest ever for this time of year. However, gas prices in many states have started decreasing, which is typical for October.

But in California, gasoline inventories are the lowest in more than 10 years — a situation made worse by the state’s strict pollution limits that require a special blend of cleaner-burning gasoline during hot summer months.

Patrick DeHaan, senior petroleum analyst at GasBuddy.com, said he is seeing the highest prices in the state around Los Angeles, where on Thursday at least five stations have crossed the $5 a gallon mark, including $5.29 in Burbank and $5.11 in Norwalk.

Prices will keep rising, he says, because in the past week wholesale gasoline prices have jumped $1 a gallon, but average retail prices have increased only 30 cents.

"This is one of the easiest forecasts: Retail prices are going to skyrocket," DeHaan said.

The jump in wholesale prices can be particularly tough on independent gas stations that often pay more for their gas because they are not part of a larger chain.

Tom Kloza, chief oil analyst at Oil Price Information Service, said he’s heard of a few California station owners shutting their pumps rather than charging the $4.90 a gallon or more necessary to break even.

"Wholesale price increases lead to retail price increases," Kloza said. "But there is some restraint among companies who do not want to exercise their current pricing power and irritate their customers."

Some analysts think prices nationally will begin to decline soon but say California could see a longer spike given its unique fuel requirements.

"Nationally, I believe most prices will wobble to and fro for the next week or so, with an eventual slow but steady attrition in retail gas prices, particularly in the Midwest and Southeast," Kloza said. "California is a wild card."

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AP Energy Writers Jonathan Fahey in New York and Sandy Shore in Denver contributed to this report.

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